1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method.
2. Description of Related Art
The following image processing apparatus has conventionally been known: when the image processing apparatus performs image processing, the image processing apparatus binarizes multiple-valued image data of a target pixel and performs error diffusion processing to diffuse errors before and after the binarization to surrounding unprocessed pixels. If such an image processing apparatus performs the error diffusion processing to a high resolution image, the throughput of the hardware thereof is large because the workload is very large.
In view of such a problem, the conventional image processing apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2002-262089 coped with the problem by blocking a plurality of pixels, adding the gradation of each pixel constituting a block, performing dither processing to the added block to binarize the inside of the block, and diffusing the errors generated at the time of the binarization to the surrounding blocks.
However, such error diffusion processing had a problem of bringing about a fuzz of a contour part (edge portion) to deteriorate an image quality at the time of outputting a character, although the operation quantity thereof was reduced and the throughput thereof was reduced.
The conventional image processing apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2002-252764 coped with such a problem by reading a plurality of pixels by the block, judging the existence of a white pixel and a black pixel in a block, obtaining an average of pixel values (gradation values) of the pixels other than the white pixel and the black pixel in the block, performing a gradation conversion, converting the converted gradation into the area gradation pattern of each pixel in the block, and forcibly converting the pixels situated at the pixel positions of the white pixel and the black pixel at the time of reading the block into the white pixel or the black pixel, respectively.
However, although the acutance of an edge portion became capable of being attained by the image processing apparatus described in Japanese Patent Application Laid-Open Publication No. 2002-252764, such reproduction of an edge portion was limited to the data of a solid image, and fuzzes appeared at a contour of a half tone image at the time of reproducing a thin line or a character.